Re: [linux-lvm] lvm on a single big partition or just a single big partition?

From: Marian Csontos <mcsontos redhat com>

To: LVM general discussion and development <linux-lvm redhat com>

Subject: Re: [linux-lvm] lvm on a single big partition or just a single big partition?

Date: Fri, 05 Jun 2009 10:00:00 +0200

Zhengquan Zhang wrote:

On Wed, Jun 03, 2009 at 02:42:29PM -0400, Stuart D. Gathman wrote:

On Wed, 3 Jun 2009, Zhengquan Zhang wrote:

For one harddrive I often create a /boot parition that is not lvm and
create a huge partition on the rest of the harddrive for PV of lvm. Now
I am thinking what is the difference between doing partition like this
and just a single big partition without lvm?

With LVM, you can create many logical volumes. If you only ever create one
logical volume that fills the entire PV, and you aren't spanning drives
(multiple PVs) or mirroring, then LVM is not doing anything for you.

Not at the moment, but the moment you run out of space and decide to add
another drive, it will save you a lot of trouble moving all your
partitions around...

That is what I am doing, so I am not fully utilizing lvm. another

question, is it advisable to create on pv for one harddrive?

Yes, it is the right way. Having 2 PVs on single drive offer no benefit
I can think of, and actually it is a step back - you can not share "free
space" between PVs, thus it is a way to simulate old fashioned partitions.

Even with just one LV, leave some space for a snapshot. Then you can
take more consistent backups by creating a snapshot of your main LV
and backing that up instead. Put your swap space in LVM as well.

Thanks for pointing out this. I never thought of leaving space for
snapshot. and the swap too, why it is good to put swap in lvm?

I think most of installers do not think of it neither (unless you
partition you disk yourself, which is not so difficult, but may be a bit
scary for newbies) - I would like an install option "leave N% of created
PV free and use only the rest now".

One reason to create multiple LVs is for virtual machines. If you
run Xen, VMWare, or other virtual machine, then each virtual machine
should have its own LVs for disk drives. This is more efficient
than using a filesystem file for a virtual disk.

Oh really, I never thought about this, so virtual machine can directly
use lv for the as their filesystem?